Suspensions of multimetal cyanide compounds, their preparation and their use

ABSTRACT

Catalyst suspensions for the ring-opening polymerization of alkylene oxides comprise a) at least one multimetal cyanide compound having a crystalline structure and a content of platelet-shaped particles of at least 30% by weight, based on the multimetal cyanide compound, and b) at least one organic complexing agent c) water and/or d) at least one polyether and/or e) at least one surface-active substance, with the proviso that at least component a) and at least two of the components b) to e) have to be present.

The present invention relates to suspensions of multimetal cyanidecompounds, their preparation and their use.

Polyether alcohols are used in large quantities for producingpolyurethanes. They are usually prepared by catalytic addition of loweralkylene oxides, in particular ethylene oxide and propylene oxide, ontoH-functional initiator substances. Catalysts used are usually basicmetal hydroxides or salts, with potassium hydroxide having the greatestindustrial importance.

In the synthesis of polyether alcohols having long chains, as are used,in particular, for producing flexible polyurethane foams, secondaryreactions occur as chain growth progresses, leading to faults in thechain structure. These by-products are referred to as unsaturatedconsituents and adversely affect the properties of the resultingpolyurethanes. There has therefore been no lack of attempts in the pastto prepare polyether alcohols having a low content of unsaturatedconstituents. In particular, the alkoxylation catalysts used have beenchanged in a targeted way in an attempt to achieve this. Thus, EP-A-268922 proposes using cesium hydroxide as catalyst. Although this doessucceed in lowering the content of unsaturated constituents, cesiumhydroxide is expensive and disposing of it is problematical.

Furthermore, the use of multimetal cyanide complexes, usually zinchexacyanometalates, for preparing polyether alcohols having a lowcontent of unsaturated constituents is known. There is a large number ofdocuments in which the preparation of polyether alcohols usingmultimetal cyanide complexes as catalysts is described. Thus, DD-A-203735 and DD-A-203 734 describe the preparation of polyetherols using zinchexacyanocobaltate.

The preparation of the zinc hexacyanometalates is also known. Thesecatalysts are usually prepared by reacting solutions of metal salts suchas zinc chloride with solutions of alkali metal or alkaline earth metalcyanometalates such as potassium hexacyanocobaltate. A water-miscible,heteroatom-containing component is generally added to the resultingsuspension immediately after the precipitation procedure. This componentcan also be present in one or both of the starting solutions. Thiswater-miscible, heteroatom-containing component can be, for example, anether, polyether, alcohol, ketone or a mixture thereof. Such processesare described, for example, in U.S. Pat. No. 3,278,457, U.S. Pat. No.3,278,458, U.S. Pat. No. 3,278,459, U.S. Pat. No. 3,427,256, U.S. Pat.No. 3,427,334, U.S. Pat. No. 3,404,109, U.S. Pat. No. 3,829,505, U.S.Pat. No. 3,941,849, EP 283,148, EP 385,619, EP 654,302, EP 659,798, EP665,254, EP 743,093, EP 755,716, U.S. Pat. No. 4,843,054, U.S. Pat. No.4,877,906, U.S. Pat. No. 5,158,922, U.S. Pat. No. 5,426,081, U.S. Pat.No. 5,470,813, U.S. Pat. No. 5,482,908, U.S. Pat. No. 5,498,583, U.S.Pat. No. 5,523,386, U.S. Pat. No. 5,525,565, U.S. Pat. No. 5,545,601, JP7,308,583, JP 6,248,068, JP 4,351,632 and U.S. Pat. No. 5,545,601.

DD-A-148 957 describes the preparation of zinc hexacyanoiridate and itsuse as catalyst in the preparation of polyether alcohols. Here,hexacyanoiridic acid is used as one starting material. This acid isisolated as a solid and is used in this form.

EP 862 947 describes the preparation of double metal cyanide complexesusing hexacyanometalic acids, in particular hexacyanocobaltic acid, ortheir aqueous solutions as starting material. The double metal cyanidesproduced as described in EP 862 947 have a high reactivity in respect ofthe ring-opening polymerization of alkylene oxides.

Although multimetal cyanide catalysts have high polymerizationactivities, there has been no lack of attempts to achieve a furtherincrease in the catalytic activity of the multimetal cyanide compounds.A major focus of work in this area is directed at multimetal cyanidecompounds which are amorphous. The preparation of such multimetalcyanide compounds is disclosed, inter alia, in EP 654,302. However, ithas been able to be shown that the activity of these catalysts can beincreased further by the incorporation of polymers. Thus, EP 700,949describes double metal cyanide complexes having an increased reactivityand containing from 5 to 80 percent by weight, based on the catalyst, ofpolyethers having a molar mass of greater than 500 dalton. WO 97/40,086describes double metal cyanide catalysts having an increased reactivityand containing from 5 to 80% by weight of polyethers having molar massesof less than 500 dalton. WO 98/16310 discloses double metal cyanideswhich contain from 2 to 80% by weight of functionalized polymers, but nopolyethers. The double metal cyanide catalysts disclosed inEP-A-700,949, WO-A-97/40,086 and WO-A-98/16,310 are generally amorphous.According to WO 98/16,310 (page 2, lines 16-22), the best double metalcyanide catalysts known at present have a low degree of crystallinity.The preferred catalysts are essentially noncrystalline (page 3, lines10-11).

Multimetal cyanide catalysts are usually used in the form of powder forpreparing polyether alcohols. U.S. Pat. No. 4,477,589 and U.S. Pat. No.4,472,560 describe suspensions of multimetal cyanide compounds inpropoxylated glycerol having contents of multimetal cyanide compound ofless than 5% by weight. U.S. Pat. No. 5,639,705 and U.S. Pat. No.5,714,639 describe catalysts in the form of pastes which comprise from10 to 60% by weight of multimetal cyanide compound, from 40 to 90% byweight of an organic complexing agent and from 1 to 20% by eight ofwater.

It is an object of the present invention to use crystalline ultimetalcyanide compounds in a form which gives them a very high catalyticactivity.

We have found that this object is achieved by suspending crystallinemultimetal cyanide compounds in organic or inorganic liquids and usingthem as catalysts in this form. It is particularly advantageous for thesuspended multimetal cyanide compound to have a platelet-likemorphology.

The present invention accordingly provides a catalyst suspension for thering-opening polymerization of alkylene oxides, comprising

-   a) at least one multimetal cyanide compound having a crystalline    structure and a content of platelet-shaped particles of at least 30%    by weight, based on the multimetal cyanide compound, and-   b) at least one organic complexing agent-   c) water and/or-   d) at least one polyether and/or-   e) at least one surface-active substance, with the proviso that at    least component a) and at least two of the components b) to e) have    to be present.

The organic complexing agent b) is selected, in particular, from thegroup consisting of alcohols, ethers, esters, ketones, aldehydes,carboxylic acids, amides, nitriles, sulfides and mixtures thereof.

As polyethers d), use is made, in particular, of polyether alcohols,preferably hydroxyl-containing polyaddition products of ethylene oxide,propylene oxide, butylene oxide, vinyloxirane, tetrahydrofuran,1,1,2-trimethylethylene oxide, 1,1,2,2-tetramethylethylene oxide,2,2-dimethyloxetane, diisobutylene oxide, α-methylstyrene oxide andmixtures thereof.

As surface-active substances e), use is made, in particular, ofcompounds selected from the group consisting of C₄-C₆₀-alcoholalkoxylates, block copolymers of alkylene oxides of differinghydrophilicity, alkoxylates of fatty acids and fatty acid glycerides,block copolymers of alkylene oxides and polymerizable acids and esters.

The crystalline multimetal cyanide compounds used according to thepresent invention are preferably prepared by the following method:

-   a) Addition of an aqueous solution of a water-soluble metal salt of    the formula M¹ _(m)(X)_(n), where M¹ is at least one metal ion    selected from the group consisting of Zn²⁺, Fe²⁺, Co³⁺, Ni²⁺, Mn²⁺,    Co²⁺, Sn²⁺, Pb²⁺, Fe³⁺, Mo⁴⁺, Mo⁶⁺, Al³⁺, V⁵⁺, Sr²⁺, W⁴⁺, W⁶⁺, Cu²⁺,    Cr²⁺, Cr³⁺, Cd²⁺, Hg²⁺, Pd²⁺, Pt²⁺, V²⁺, Mg²⁺, Ca²⁺, Ba²⁺ and    mixtures thereof,-   X is at least one anion selected from the group consisting of    halide, hydroxide, sulfate, carbonate, cyanide, thiocyanate,    isocyanate, carboxylate, in particular formate, acetate, propionate    or oxalate, and nitrate and m and n are integers which satisfy the    valences of M¹ and X,-   to an aqueous solution of a cyanometalate compound of the formula    HaM²(CN)_(b)(A)_(c), where M² is at least one metal ion selected    from the group consisting of Fe²⁺, Fe³⁺, Co³⁺, Cr³⁺, Mn²⁺, Mn³⁺,    Rh³⁺, Ru²⁺, Ru³⁺, V⁴⁺, V⁵⁺, Co²⁺, Ir³⁺ and Cr²⁺ and M² can be    identical to or different from M¹,-   H is hydrogen or a metal ion, usually an alkali metal ion, an    alkaline earth metal ion or an ammonium ion,-   A is at least one anion selected from the group consisting of    halide, hydroxide, sulfate, carbonate, cyanate, thiocyanide,    isocyanate, carboxylate and nitrate, in particular cyanide, where A    can be identical to or different from X, and a, b and c are integers    selected so that the cyanide compound is electrically neutral,-   where one or both solutions may, if desired, comprise at least one    water-miscible, heteroatom-containing ligand selected from the group    consisting of alchols, ethers, esters, ketones, aldehydes,    carboxylic acids, amides, sulfides or mixtures of at least two of    the compounds mentioned,-   and at least one of the two solutions comprises a surface-active    substance,-   b) if desired, combination of the aqueous suspension formed in    step a) with a water-miscible, heteroatom-containing ligand selected    from the above-described group which can be identical to or    different from the ligand in step a),-   c) if desired, separation of the multimetal cyanide compound from    the suspension.

The platelet-like multimetal cyanide compounds used according to thepresent invention are crystalline and can have a cubic, tetragonal,trigonal, orthorhombic, hexagonal, monoclinic or triclinic crystalstructure. The definition of the crystal systems describing thesestructures and the space groups belonging to the abovementioned crystalsystems may be found in “International tables for crystallography”,Volume A, editor: Theo Hahn, (1995).

For the preparation of multimetal cyanide compounds which are used forthe suspensions of the present invention, it is advantageous, but notnecessary, to use the cyanometalic acid as cyanometalate compound, sincethis does not result in unavoidable formation of a salt as by-product.

These cyanometalic acids (hydrogen cyanometalates) which are preferablyused are stable and-readily handleable in aqueous solution. They can beprepared, for example as described in W. Klemm, W. Brandt, R. Hoppe, Z.Anorg. Allg. Chem. 308, 179 (1961), starting from the alkali-metalcyanometalate via the silver cyanometalate and then to the cyanometalicacid. A further possibility is to convert an alkali metal or alkalineearth metal cyanometalate into a cyanometalic acid by means of an acidion exchanger, as described, for example, in F. Hein, H. Lilie, Z.Anorg. Allg. Chem. 270, 45 (1952), or A. Ludi, H. U. Gudel, V. Dvorak,Helv. Chim. Acta 50, 2035 (1967). Further possible ways of synthesizingthe cyanometalic acids may be found, for example, in “Handbuch derPräparativen Anorganischen Chemie”, G. Bauer (editor), Ferdinand EnkeVerlag, Stuttgart, 1981. For an industrial preparation of thesecompounds, as is necessary for the process of the present invention, thesynthesis via ion exchangers is the most advantageous route. After theyhave been synthesized, the cyanometalic acid solutions can be processedfurther immediately, but it is also possible to store them for arelatively long period. Such storage should be carried out in theabsence of light to prevent decomposition of the acid.

The proportion of the acid in the solution should be greater than 80% byweight, based on the total mass of cyanometalate complexes, preferablygreater than 90% by weight, in particular greater than 95% by weight.

As heteroatom-containing ligands, use is made of the above-describedorganic substances. In a preferred embodiment of the preparationprocess, no heteroatom-containing ligand is added to the solutions instep a) and the addition of heteroatom-containing ligand to thesuspension of precipitate is also omitted in step b). Only at least onesurface-active compound is added, as mentioned above, to one or both ofthe solutions in step a).

The surface-active compounds used according to the present invention canbe anionic, cationic, nonionic and/or polymeric surfactants.

In particular, nonionic and/or polymeric surfactants are used. Compoundsselected from this group are, in particular, fatty alcohol alkoxylates,block copolymers of various epoxides having differing hydrophilicity,castor oil alkoxylates or block copolymers of epoxides and othermonomers, e.g. acrylic acid or methacrylic acid.

Fatty alcohol alkoxylates used according to the present invention have afatty alcohol comprising 8-36 carbon atoms, in particular 10-18 carbonatoms. This is alkoxylated with ethylene oxide, propylene oxide and/orbutylene oxide. The polyether part of the fatty alcohol alkoxylate usedaccording to the present invention can consist of pure ethylene oxide,propylene oxide or butylene oxide polyethers. Furthermore, it is alsopossible to use copolymers of two or three different alkylene oxides orelse block copolymers of two or three different alkylene oxides. Fattyalcohol alkoxylates which have pure polyether chains are, for example,Lutensol AO grades from BASF AG. Fatty alcohol alkoxylates having blockcopolymers as polyether part are Plurafac LF grades from BASFAktiengesellschaft. The polyether chains particularly preferably consistof from 2 to 50, in particular from 3 to 15, alkylene oxide units.

Block copolymers as surfactants comprise two different polyether blockswhich differ in their hydrophilicity. Block copolymers which can be usedaccording to the present invention may comprise ethylene oxide andpropylene oxide (Pluronic grades, BASF Aktiengesellschaft). The watersolubility is controlled via the lengths of the various blocks. Themolar masses are in the range from 500 Da to 20,000 Da, preferably from1000 Da to 6000 Da and in particular 1500-4000 Da. In the case ofethylene-propylene copolymers, the proportion of ethylene oxide is from5 to 50% by weight and the proportion of propylene oxide is from 50 to95% by weight.

Copolymers of alkylene oxide with other monomers which can be usedaccording to the present invention preferably have ethylene oxideblocks. The other monomer can be, for example, butyl methacrylate(PBMA/PEO BE1010/BE1030, Th. Goldschmidt), methyl methacrylate (PMMA/PEOME1010/ ME1030, Th. Goldschmidt) or methacrylic acid (EA-3007, Th.Goldschmidt).

The surface-active substances used should have a moderate to goodsolubility in water.

To prepare the crystalline multimetal cyanide compounds used accordingto the present invention, an aqueous solution of a cyanometalic acid orof a cyanometalate salt is combined with the aqueous solution of a metalsalt of the formula M¹ _(m)(X)_(n), where the symbols are as definedabove. Here, a stoichiometric excess of the metal salt is employed. Themolar ratio of the metal ion to the cyanometalate component ispreferably from 1.1 to 7.0, more preferably from 1.2 to 5.0 andparticularly preferably from 1.3 to 3.0. It is advantageous to place themetal salt solution in the precipitation vessel first and to add thecyanometalate compound, but the reverse procedure can also be used.During and after combining the starting solutions, good mixing, forexample by stirring, is necessary.

The content of the cyanometalate compound in the cyanometalate startingsolution based on the mass of cyanometalate starting solution is from0.1 to 30% by weight, preferably from 0.1 to 20% by weight, inparticular from 0.2 to 10% by weight. The content of the metal saltcomponent in the metal salt solution based on the mass of metal saltsolution is from 0.1 to 50% by weight, preferably from 0.2 to 40% byweight, in particular from 0.5 to 30% by weight.

The surface-active substances are generally added beforehand to at leastone of the two solutions. The surface-active substances are preferablyadded to the solution which is initially charged in the precipitation.The content of surface-active substances in the precipitation solutionbased on the total mass of the precipitation suspension is from 0.01 to40% by weight. Preference is given to a content of from 0.05 to 30% byweight.

A further preferred embodiment provides for the surface-activesubstances to be divided proportionately among the two startingsolutions.

The heteroatom-containing ligands are, in particular, added to thesuspension formed after combination of the two starting solutions. Heretoo, good mixing has to be ensured.

However, it is also possible to add all or some of the ligand to one orboth starting solutions. In this case, owing to the change in the saltsolubility, the ligand is preferably added to the solution of thecyanometalate compound.

The content of the ligand in the suspension formed after theprecipitation should be from 1 to 60% by weight, preferably from 5 to40% by weight, in particular from 10 to 30% by weight.

The multimetal cyanide compounds used according to the present inventionpreferably have X-ray diffraction patterns as are shown in FIGS. 3 and 4of DE 197 42 978.

The multimetal cyanide compounds used for preparing the suspensions ofthe present invention preferably comprise primary crystals having aplatelet-like habit.

For the purposes of the present invention, platelet-shaped particles areparticles whose thickness is one third, preferably one fifth,particularly preferably one tenth, of their length and width. Thepreferred catalyst according to the present invention contains more than30% by weight of such platelet-shaped crystals, preferably more than 50%by weight, particularly preferably more than 70% by weight and veryparticularly preferably more than 90% by weight. The preferredmultimetal cyanide compounds according to the present invention can beseen in scanning electron micrographs.

Multimetal cyanide compounds which are less preferred according to thepresent invention are often either in rod form or in the form of smallcube-shaped or spherical crystals.

Depending on how pronounced the platelet character of the particles isand how many are present in the catalyst, it is possible that distinctto strong intensity changes in the individual reflections in the X-raydiffraction pattern compared to rod-shaped multimetal cyanide compoundsof the same structure will occur.

The multimetal cyanide compounds produced by precipitation according tothe above-described process can then be separated from the suspension byfiltration or centrifugation. After the separation, the multimetalcyanide compounds can then be washed one or more times. Washing can becarried out using water, the abovementioned heteroatom-containingligands or mixtures thereof. Washing can be carried out in theseparation apparatus (e.g. filtration apparatus) itself or be carriedout in separate apparatuses by, for example, resuspension of themultimetal cyanide compound in the washing liquid and separating it fromthe liquid again. This washing can be carried out at from 10° C. to 150°C., preferably from 15 to 60° C.

The multimetal cyanide compound can subsequently be dried at from 30° C.to 180° C. and pressures of from 0.001 bar to 2 bar, preferably from 30°C. to 100° C. and pressures of from 0.002 bar to 1 bar.

Drying can also be omitted, in which case a moist filter cake isobtained.

A preferred embodiment of the preparation process for the multimetalcyanide compound used according to the present invention provides for noorganic, heteroatom-containing ligand, as has been defined above, apartfrom the surface-active substance to be added before, during or afterthe precipitation. In this embodiment of the preparation process, inwhich no further organic, heteroatom-containing ligands apart from thesurface-active substance area used, the multimetal cyanide compound iswashed with water after separation from the precipitation suspension.

The multimetal cyanide compounds prepared as described above are used inthe form of the suspensions of the present invention for preparingpolyether alcohols.

Both the moist and the dried multimetal cyanide compounds can be used asstarting materials for the suspensions of the present invention.

The pulverulent, dried multimetal cyanide compounds are, to prepare thesuspensions of the present invention, dispersed as finely as possible inthe suspension liquid by an efficient dispersion procedure in order toachieve a very high activity of the multimetal cyanide catalyst.

Such methods of efficiently producing a very finely dispersed suspensionare, inter alia, stirring under high shear forces, e.g. in homogenizersor Ultraturrax apparatuses, and also the use of dispersion machines, inparticular ball mills and agitated ball mills, e.g. bead mills ingeneral and particularly those having small milling beads (e.g. 0.3 mmdiameter) such as the double-cylinder bead mills (DCP-Super Flow®) fromDraiswerken GmbH, Mannheim, or the centrifugal fluidized bed mills fromNetzsch Geratebau GmbH, Selb. If desired, dissolvers can be used forpredispersion. Furthermore, small amounts of dispersants known to thoseskilled in the art, e.g. lecithin, zinc oleate or zinc stearate, can beused. In addition, all methods which allow the powder to be dispersedvery finely in liquids are suitable.

Dispersion can be carried out at from 10° C. to 150° C., preferably from30° C. to 120° C.

Dispersion liquids which can be used are polyethers, organic liquids orwater, and also mixtures thereof.

As polyethers, it is possible to use compounds having molar masses offrom 150 to 6000 dalton and functionalities of from 1 to 8. Preferenceis given to using polyethers having molar masses of from 150 to 2000dalton and functionalities of from 1 to 3, in particular molar masses offrom 150 to 800 dalton.

If the predried multimetal cyanide compound is suspended in an organicliquid, suspensions having solids contents of less than 10% by weightare preferred. Particular preference is given to solids contents of lessthan 5% by weight. Organic liquids which can be used areheteroatom-containing compounds and also hydrocarbons or mixturesthereof. Compounds which have a vapor pressure of greater than 0.005 barat 100° C.

If the predried multimetal cyanide compound is suspended in water,preference is given to suspensions having solids contents of less than20% by weight and pastes having solids contents of less than 60% byweight. The water content of the pastes and suspensions should then beabove 20% by weight.

Preference is given to omitting the drying step. In this case, the moistmultimetal cyanide compounds are used for preparing the suspensions ofthe present invention.

For this purpose, a suspension is prepared from the moist ultimetalcyanide compound after precipitation and separation of the precipitatefrom the suspension and after washing of the multimetal cyanidecompound, either on the filtration apparatus or externally withfiltration being repeated again, but without carrying out a drying step.The multimetal cyanide compound can, as in the case of the driedmultimetal cyanide compounds, be suspended in the abovementioneddispersion media. The methods of preparing a very finely dividedsuspension which have been described for the dried multimetal cyanidecompounds can also be used for dispersing the undried multimetal cyanidecompounds.

When using moist multimetal cyanide compounds for preparing suspensionsin at least one polyether or a similarly high-boiling liquid, heat andvacuum can, in a preferred embodiment, be applied simultaneously duringthe dispersion step in order to remove volatile constituents such aswater or organic ligands. In the present context, application of vacuummeans both the normal vacuum stripping at pressures down to 0.001 barand also the combination of vacuum treatment and stripping with inertgases such as nitrogen, argon, helium, etc. The temperature in this stepcan be from 10° C. to 150° C., preferably from 30° C. to 120° C.

In the case of multimetal cyanide suspensions in polyethers, suspensionshaving solids contents of less than 20% by weight are preferred.Particular preference is given to solids contents of less than 10% byweight, in particular less than 5% by weight. If the undried multimetalcyanide compound is suspended in organic liquids, as described above,suspensions having solids contents of less than 10% by weight arepreferred. Particular preference is given to solids contents of lessthan 5% by weight. If the undried multimetal cyanide compound issuspended in water, suspensions having solids contents of less than 20%by weight and pastes having solids contents of less than 60% by weightare preferred. The water content of the pastes and suspensions shouldthen be above 20% by weight.

If the starting materials used for preparing the multimetal cyanidecompound are cyanometalic acid and, as metal salt, a salt of an acidwhich has a vapor pressure of greater than 0.005 bar at 100° C., thesuspensions of the present invention can be prepared according to thefollowing advantageous embodiment. Here, the precipitation is carriedout in the presence of the surface-active agent and optionally theorganic ligand. If an organic ligand is used, the organic ligand shouldlikewise have a vapor pressure of greater than 0.005 bar at 100° C.After combining the starting material solutions, polyether is added tothe precipitation suspension and the acid formed during theprecipitation, the water and at least part of the organic ligands aredistilled off, if desired under reduced pressure. The remainingsuspension has, according to the present invention, a solids content ofless than 20% by weight and a polyether content of greater than 80% byweight. The possible polyethers are defined above. Preference is givento polyether alcohols having molar masses of from 150 to 2000 dalton, sothat the resulting suspension can be used directly as catalyst forpreparing polyether alcohols.

The multimetal cyanide suspensions prepared by the method according tothe present invention are very useful as catalysts for the synthesis ofpolyetherols having functionalities of from 1 to 8, preferably from 1 to6, and molar masses of from 500 to 50,000, preferably from 800 to15,000, by addition of alkylene oxides onto H-functional initiatorsubstances. The catalyst concentrations employed are less than 1% byweight, preferably less than 0.5% by weight, particularly preferablyless than 1000 ppm, very particularly preferably less than 500 ppm andespecially preferably less than 100 ppm, based on the total mass of thepolyetherol. The polyetherols can be prepared either continuously orbatchwise. The synthesis is carried out by a suspension process. Thetemperatures employed in the synthesis are in the range from 50° C. to200° C., with preference being given to temperatures in the range from90° C. to 150° C.

To prepare polyether alcohols using the catalysts of the presentinvention, it is possible to employ compounds having at least onealkylene oxide group, for example ethylene oxide, 1,2-epoxypropane,1,2-methyl-2-methylpropane, 1,2-epoxybutane, 2,3-epoxybutane,1,2-methyl-3-methylbutane, 1,2-epoxypentane, 1,2-methyl-3-methylpentane,1,2-epoxyhexane, 1,2-epoxyheptane, 1,2-epoxyoctane, 1,2-epoxynonane,1,2-epoxydecane, 1,2-epoxyundecane, 1,2-epoxydodecane, styrene oxide,1,2-epoxycyclopentane, 1,2-epoxycyclohexane, (2,3-epoxypropyl)-enzene,vinyloxirane, 3-phenoxy-1,2-epoxypropane, 2,3-epoxy(methyl ether),2,3-epoxy(ethyl ether), 2,3-epoxy(isopropyl ether),2,3-epoxy-1-propanol, 3,4-epoxybutyl stearate, 4,5-epoxypentyl acetate,2,3-epoxy propyl methacrylate, 2,3-epoxypropyl acrylate, gylcidylbutyrate, methyl glycidate, thyl 2,3-epoxybutanoate,4-(trimethylsilyl)butane 1,2-epoxide, 4-(triethylsilyl)butane1,2-epoxide, 3-(perfluoromethyl)propene oxide, 3-(perfluoroethyl)propeneoxide, 3-(perfluorobutyl)propene xide, 4-(2,3-epoxypropy)morpholine,1-(oxiran-2-ylmethyl)-yrrolidin-2-one, and also any mixtures of at leasttwo of the bovementioned compounds.

Preference is given to ethylene oxide, 1,2-epoxypropane,1,2-epoxybutane, styrene oxide, vinyloxirane and any mixtures of these,in particular ethylene oxide, 1,2-epoxypropane and mixtures of ethyleneoxide and 1,2-epoxypropane.

The invention is illustrated by the following examples.

EXAMPLES Preparation of Hexacyanocobaltic Acid

7 l of strong acid ion exchanger in the sodium form (Amberlite® 252 Na,Rohm & Haas) were introduced into an ion exchange column (length: 1 m,volume: 7.7 l). The ion exchanger was subsequently converted into the Hform by passing 10% strength hydrochloric acid through the ion exchangecolumn for 9 hours at a rate of 2 bed volumes per hour, until the sodiumcontent of the discharged solution was less than 1 ppm. The ionexchanger was subsequently washed with water until neutral. Theregenerated ion exchanger was then used to prepare a hexacyanocobalticacid which was essentially free of alkali metal. For this purpose, a0.24 molar solution of potassium hexacyanocobaltate in water was passedthrough the ion exchanger at a rate of 1 bed volume per hour. After 2.5bed volumes, the feed was changed from potassium hexacyanocobaltatesolution to water. The 2.5 bed volumes obtained had an averagehexacyanocobaltic acid content of 4.5% by weight and alkali metalcontents of less than 1 ppm. The hexacyanocobaltic acid solutions usedfor the further examples were diluted appropriately with water.

Comparative Example 1

200 ml of an aqueous hexacyanocobaltic acid solution (4.4% by weight ofH₃[Co(CN)₆], potassium content <1 ppm) were heated to 40° C. andsubsequently admixed while stirring (blade stirrer, rotational speed=500min⁻¹) with a solution of 17.88. g of zinc(II) acetate dihydrate in 60 gof water. Subsequently, 35 g of tert-butanol were added to thesuspension. The suspension was stirred for a further 30 minutes at 40°C. The solid was then filtered off with suction and washed on the filterwith 200 ml of tert-butanol. The solid which had been treated in thisway was dried at 50° C. under reduced pressure for 16 hours. The x-raydiffraction pattern of the double metal cyanide obtained in this waycould be indexed as monoclinic; the scanning electron micrographs showedrod-shaped particles.

Comparative Example 2

300 ml of an aqueous hexacyanocobaltic acid solution (2.2% by weight ofH₃[Co(CN)₆], potassium content <1 ppm) were heated to 40° C. and whilestirring (blade stirrer, rotational speed=500 min⁻¹), 15 ml of PluronicPE 6100 (BASF Aktiengesellschaft, block copolymer of PO and EO) wereadded and dissolved. Subsequently, a solution of 13.38 g of zinc(II)acetate dihydrate in 50 g of water was added while stirring (bladestirrer, rotational speed=500 min⁻¹). 50 g of tert-butanol weresubsequently added to the suspension. The suspension was stirred for afurther 30 minutes at 40° C. The solid was then filtered off withsuction and washed on the filter with 200 ml of tert-butanol. The solidwhich had been treated in this way was dried at 50° C. under reducedpressure for 16 hours. The X-ray diffraction pattern of the double metalcyanide obtained in this way showed two phases of which one could beindexed as monoclinic and the other could be indexed as cubic; thescanning electron micrographs showed relatively large platelet-shapedparticles and traces of small cubic particles.

Comparative Example 3

300 g of an aqueous hexacyanocobaltic acid solution (2.2% by weight ofH₃[Co(CN)₆], potassium content <1 ppm) were heated to 40° C. and whilestirring (blade stirrer, rotational speed=500 min⁻¹ ), 30 ml of PluronicPE 6100 (BASF Aktiengesellschaft, block copolymer of PO and EO) wereadded and dissolved. Subsequently, a solution of 13.38 g of zinc(II)acetate dihydrate in 50 g of water was added while stirring (bladestirrer, rotational speed=500 min⁻¹). 50 g of tert-butanol weresubsequently added to the suspension. The suspension was stirred for afurther 30 minutes at 40° C. The solid was then filtered off withsuction and washed on the filter with 200 ml of tert-butanol. The solidwhich had been treated in this way was dried at 50° C. under reducedpressure for 16 hours. The X-ray diffraction pattern of the double metalcyanide obtained in this way showed two phases of which one could beindexed as monoclinic and the other could be indexed as cubic; thescanning electron micrographs showed relatively large platelet-shapedparticles and traces of small cubic particles.

Comparative Example 4

200 g of an aqueous hexacyanocobaltic acid solution (3.7% by weight ofH₃[Co(CN)₆], potassium content <1 ppm) were heated to 40° C. and whilestirring (blade stirrer, rotational speed=500 min⁻¹), 0.5 ml of PlurafacLF 400 (BASF Aktiengesellschaft) was added and dissolved. Subsequently,a solution of 14.9 g of zinc(II) acetate dehydrate in 60 g of water wasadded while stirring (blade stirrer, rotational speed=500 min⁻¹). 35 gof tert-butanol were subsequently added to the suspension. Thesuspension was stirred for a further 30 minutes at 40° C. The solid wasthen filtered off with suction and washed on the filter with 200 ml oftert-butanol. The solid which had been treated in this way was dried at50° C. under reduced pressure for 16 hours. The X-ray diffractionpattern of the double metal cyanide obtained in this way showed onecrystalline phase which could be indexed as monoclinic; the scanningelectron micrographs showed platelet-shaped particles.

Example 1

300 g of an aqueous hexacyanocobaltic acid solution (2.2% by weight ofH₃[Co(CN)₆], potassium content<1 ppm) were heated to 40° C. and whilestirring (blade stirrer, rotational speed=500 min⁻¹), 10 ml of PluronicPE 6100 (BASF Aktiengesellschaft) were added and dissolved. A solutionof 13.38 g of zinc(II) acetate dihydrate in 50 g of water wassubsequently added while stirring (blade stirrer, rotational speed=500min⁻¹). 35 g of dipropylene glycol were subsequently added to thesuspension. The suspension was stirred for a further 30 minutes at 40°C. The solid was then filtered off with suction and washed on the filterwith 200 ml of dipropylene glycol. The moist solid was treated at 50° C.under reduced pressure for 16 hours and subsequently dispersed whilestill moist in dipropylene glycol to give a 20% strength suspension.

Example 2

479.3 g of an aqueous zinc acetate solution (13.38 g of zinc acetatedihydrate and 2.2 g of Pluronice PE 6200 (BASF Aktiengesellschaft)dissolved in 150 g of water) were heated to 50° C. While stirring (screwstirrer, stirring energy input: 1W/l), 558 g of an aqueoushexacyanocobaltic acid solution (cobalt content: 9 g/l, 1.5% by weightof Pluronic® PE 6200 (BASF 45 Aktiengesellschaft), based on thehexacyanocobaltic acid solution) were then metered in over a period of20 minutes. After all the hexacyanocobaltic acid solution had beenmetered in, the mixture was stirred for a further 5 minutes at 50° C.The temperature was subsequently reduced to 40° C. over a period of onehour. The precipitated solid was separated from the liquid by means of apressure filter and washed with water. The moist filter cake wassubsequently dispersed in the amount of water required to give a 5%strength by weight multimetal cyanide suspension.

Example 3

The synthesis was carried out in a cleaned and dried 1 l stirringautoclave. 150 g of polypropylene glycol were placed in the stirringautoclave and admixed with 80 ppm of multimetal cyanide catalyst fromExample 2 (content of solid multimetal cyanide compound, based on themass of final product). The contents of the reactor were made inert withnitrogen and treated at 127° C. under reduced pressure for 1.25 hours.

Subsequently, 1 mol of propylene oxide was metered in at 130° C. and thestart of the reaction was awaited. Subsequently, the remaining propyleneoxide up to a total amount of 620 g was metered in. The addition timewas 3 hours and the pressure maximum was 4 bar absolute. The product wasworked up by vacuum distillation and filtration.

Hydroxyl number: 57 mg KOH/g; Viscosity at 25° C.: 320 mPas; Zn/Cocontent: 4.1/<1 ppm.

Comparative Example 5

The synthesis was carried out in a cleaned and dried 1 l stirringautoclave. 200 g of polypropylene glycol were placed in the stirringautoclave and admixed with 250 ppm of catalyst from ComparativeExample 1. The contents of the reactor were made inert with nitrogen andtreated at 108° C. under reduced pressure for 1 hour.

1 mol of propylene oxide was subsequently metered in at 115° C. and thestart of the reaction was awaited. Subsequently, the remaining propyleneoxide up to a total amount of 800 g was metered in. The addition timewas 1.1 hours and the pressure maximum was 3.9 bar absolute. The productwas worked up by vacuum distillation and filtration.

Hydroxyl number: 52 mg KOH/g; Viscosity at 25° C.: 516 mPas; Zn/Cocontent: 62/25 ppm.

Example 4

The synthesis was carried out in a cleaned and dried 1 l stirringautoclave. 200 g of polypropylene glycol were placed in the stirringautoclave and admixed with 100 ppm of catalyst from Example 1. Thecontents of the reactor were made inert with nitrogen and treated at105° C. under reduced pressure for 1 hour. 1 mol of propylene oxide wassubsequently metered in at 110° C. and the start of the reaction wasawaited. Subsequently, the remaining propylene oxide up to a totalamount of 800 g was metered in. The addition time was 1.6 hours and thepressure maximum was 4.2 bar absolute. The product was worked up byvacuum distillation and filtration.

Hydroxyl number: 53 mg KOH/g; Viscosity at 25° C.: 571 mPas; Zn/Cocontent: 2.7/<2 ppm.

Comparative Example 6

The synthesis was carried out in a cleaned and dried 1 l stirringautoclave. 200 g of polypropylene glycol were placed in the stirringautoclave and admixed with 125 ppm of catalyst from Comparative Example3. The contents of the reactor were made inert with nitrogen and treatedat 105° C. under reduced pressure for 1 hour.

1 mol of propylene oxide was subsequently metered in at 115° C. and thestart of the reaction was awaited. Subsequently, the remaining propyleneoxide up to a total amount of 800 g was metered in. The addition timewas 0.75 hour and the pressure maximum was 4.1 bar absolute. The productwas worked up by vacuum distillation and filtration.

Hydroxyl number: 56 mg KOH/g; Viscosity at 25° C.: 470 mPas; Zn/Cocontent: 6.5/2.2 ppm.

Comparative Example 7

The synthesis was carried out in a cleaned and dried 1 l stirringautoclave. 200 g of polypropylene glycol were placed in the stirringautoclave and admixed with 125 ppm of catalyst from Comparative Example3. The contents of the reactor were made inert with nitrogen and treatedat 105° C. under reduced pressure for 1 hour.

1 mol of propylene oxide was subsequently metered in at 115° C. and thestart of the reaction was awaited. Subsequently, the remaining propyleneoxide up to a total amount of 800 g was metered in. The addition timewas 1 hour and the pressure maximum was 4.6 bar absolute. The productwas worked up by vacuum distillation and filtration.

Hydroxyl number: 53 mg KOH/g; Viscosity at 25° C.: 337 mPas; Zn/Cocontent: 14/5.2 ppm.

1-12. (canceled)
 13. A process for preparing polyether alcohols byring-opening polymerization of alkylene oxides in the presence of acatalyst suspension comprising: a) at least one multimetal cyanidecompound having a crystalline structure and a content of platelet-shapedparticles of at least 30% by weight, based on the multimetal cyanidecompound, and/or b) at least one organic complexing agent c) waterand/or d) at least one polyether and e) at least one surface-activesubstance, with the proviso that at least components a), d) and e) andat least one of the components b) and c) have to be present wherein d)and e) are not the same components.
 14. (canceled)
 15. A process forpreparing polyether alcohols as set forth in claim 13, wherein the atleast one multimetal cyanide compound a) has a cubic crystal structure.16. A process for preparing polyether alcohols as set forth in claim 13,wherein the at least one multimetal cyanide compound a) has a tetragonalcrystal structure.
 17. A process for preparing polyether alcohols as setforth in claim 13, wherein the at least one multimetal cyanide compounda) has an orthorhombic crystal structure.
 18. A process for preparingpolyether alcohols as set forth in claim 13, wherein the at least onemultimetal cyanide compound a) has a hexagonal crystal structure.
 19. Aprocess for preparing polyether alcohols as set forth in claim 13,wherein the at least one multimetal cyanide compound a) has a trigonalcrystal structure.
 20. A process for preparing polyether alcohols as setforth in claim 13, wherein the at least one multimetal cyanide compounda) has a monoclinic crystal structure.
 21. A process for preparingpolyether alcohols as set forth in claim 13, wherein the at least onemultimetal cyanide compound a) has a triclinic crystal structure.
 22. Aprocess for preparing polyether alcohols as set forth in claim 13,wherein the organic complexing agent b) is selected from the groupconsisting of alcohols, ethers, esters, ketones, aldehydes, carboxylicacids, amides, nitriles, sulfides and mixtures thereof.
 23. A processfor preparing polyether alcohols as set forth in claim 13, wherein thepolyether d) is a polyetherol.
 24. A process for preparing polyetheralcohols as set forth in claim 23, wherein the polyetherol is selectedfrom the group consisting of hydroxyl-containing polyaddition productsof ethylene oxide, propylene oxide, butylene oxide, vinyloxirane,tetrahydrofuran, 1,1,2-trimethylene oxide, diisobutylene oxide,α-methylstyrene oxide, and mixtures thereof.
 25. A process for preparingpolyether alcohols as set forth in claim 13, wherein the surface-activesubstances e) are selected from the group consisting of C₄-C₆₀-alcoholalkoxylates, block copolymers of alkylene oxides of differinghydrophilicity, alkoxylates of fatty acids and fatty acid glycerides,block copolymers of alkylene oxides and polymerizable acids and esters.26. A process for preparing polyether alcohols as set forth in claim 13,wherein the content of the platelet-shaped particles includes primaryparticles having a length and a width that are at least three timesgreater than a thickness of the primary particles.
 27. A polyetheralcohol prepared as claimed in claim 13.